<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <button id="btn">显示/隐藏</button>
    <div id="box">text...</div>
    <script>
      const btn = document.getElementById("btn");
      const box = document.getElementById("box");

      btn.onclick = function () {
        if (box.style.display === "none") {
          box.style.display = "";
        } else {
          box.style.display = "none";
        }
      };
    </script>
  </body>
</html>
